Syntheses, Structures, and Reactivities of ... - ACS Publications

Hiroshige Ishino, Tatsuya Nagano, Shigeki Kuwata, Youhei Yokobayashi,. Youichi Ishii,* and Masanobu Hidai*,†. Department of Chemistry and Biotechnol...
31 downloads 0 Views 180KB Size
Download PDF
188

Organometallics 2001, 20, 188-198

Syntheses, Structures, and Reactivities of Heterobimetallic Bridging Dinitrogen Complexes Containing Group 6 and Group 4 or 5 Transition Metals1 Hiroshige Ishino, Tatsuya Nagano, Shigeki Kuwata, Youhei Yokobayashi, Youichi Ishii,* and Masanobu Hidai*,† Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Yasushi Mizobe Institute of Industrial Science, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106-8558, Japan Received August 8, 2000

A series of heterobimetallic dinitrogen complexes containing group 6 and group 4 or 5 transition metals were synthesized by the reaction of the tungsten or molybdenum dinitrogen complexes cis-[W(N2)2(PMe2Ph)4] (1) and trans-[M(N2)2(dppe)2] (2) (M ) W, Mo) with group 4 or group 5 compounds such as [CpTiCl3], [Cp2M′Cl2] (M′ ) Ti, Zr, Hf), or [Cp′M′Cl4] (Cp′ ) Cp, Cp*; M′ ) Nb, Ta). Crystallographic studies of the complexes thus obtained including [WCl(PMe2Ph)4(µ-N2)TiCpCl2] and [WCl(PMe2Ph)4(µ-N2)NbCpCl3] revealed that the M-NN-M′ core is essentially linear, and the N-N bond is regarded to have the formal bond order of 2. Several µ-N2 complexes with methyl ligands at the group 4 or 5 metal center were also obtained through the reaction of dinitrogen complexes 1 and 2a (M ) W) with the methyl complexes [Cp2ZrMeCl], [TaMe3Cl2], and [NbMe2Cl3]. The reaction of the complex [WCl(dppe)2(µ-N2)TiCpCl2] with Li2S5 afforded the η2-pentasulfido complex [WCl(dppe)2(µN2)TiCpS5], where the η2-S5 ligand forms a six-membered chelate ring with the chair conformation. Protonation of the µ-N2 complexes having PMe2Ph ligands gave NH3 in moderate yield, concurrent with the formation of a small amount of NH2NH2. Introduction Activation and chemical transformation of molecular dinitrogen at metal centers under mild conditions have been the subject of current attention.2-7 In particular, recent advances in the studies on the active site of nitrogenase8 have aroused intense interest in properties and reactivities of dinitrogen bound at multinuclear transition metal centers, and intriguing reactivities of multinuclear µ-N2 complexes have been found which include the N-N fission.9-12 However, most of the µ-N2 † Present address: Department of Materials Science and Technology, Faculty of Industrial Science and Technology, Science University of Tokyo, Noda, Chiba 278-8510, Japan. E-mail: [email protected]. sut.ac.jp. (1) Preparation and Properties of Molybdenum and Tungsten Dinitrogen Complexes. 70. Part 69: Nishibayashi, Y.; Takemoto, S.; Iwai, S.; Hidai, M. Inorg. Chem., in press. (2) Hidai, M.; Mizobe, Y. Chem. Rev. 1995, 95, 1115-1133. (3) Gambarotta, S. J. Organomet. Chem. 1995, 500, 117-126. (4) Bazhenova, T. A.; Silov, A. E. Coord. Chem. Rev. 1995, 95, 69145. (5) Hidai, M.; Mizobe, Y. In Molybdenum Enzymes, Cofactors and Model Systems; Stiefel, E. I., Coucouvanis, D., Newton, W. E., Eds.; American Chemical Society: Washington, DC, 1993; pp 346-362. (6) Leigh, G. J. Acc. Chem. Res. 1992, 25, 177-181. (7) Hidai, M.; Mizobe, Y. In Reactions of Coordinated Ligands; Braterman, P. S., Ed.; Plenum Press: New York, 1989; Vol. 2, pp 53114. (8) Howard, J. B.; Rees, D. C. Chem. Rev. 1996, 96, 2965-2982. (9) Caselli, A.; Solari, E.; Scopelliti, R.; Floriani, C.; Re, N.; Rizzoli, C.; Chiesi-Villa, A. J. Am. Chem. Soc. 2000, 122, 3652-3670. (10) Clentsmith, G. K. B.; Bates, V. M. E.; Hitchcock, P. B.; Cloke, G. N. J. Am. Chem. Soc. 1999, 121, 10444-10445.

complexes investigated so far are homobimetallic compounds, and the chemistry of heterobimetallic dinitrogen complexes still remains to be explored. In fact, the structurally characterized µ-N2 complexes containing two different transition metals have been very limited in number.11,13-19 In the course of our continuous study on reactivities of the molybdenum and tungsten dinitrogen complexes such as cis-[W(N2)2(PMe2Ph)4] (1) and trans-[M(N2)2(dppe)2] (dppe ) Ph2PCH2CH2PPh2) (2a, M ) W; 2b, M ) Mo), we have previously found that the coordinated dinitrogen in this type of tungsten complexes is attacked by Lewis acids including not only group 13 metal (B,20 (11) Peters, J. C.; Cherry, J.-P. F.; Thomas, J. C.; Baraldo, L.; Mindiola, D. J.; Davis, W. M.; Cummins, C. C. J. Am. Chem. Soc. 1999, 121, 10053-10067. (12) Berno, P.; Gambarotta, S. Angew. Chem., Int. Ed. Engl. 1995, 34, 822-824. (13) Mindiola, D. J.; Meyer, K.; Cherry, J.-P. F.; Baker, T. A.; Cummins, C. C. Organometallics 2000, 19, 1622-1624. (14) O’Donoghue, M. B.; Davis, W. M.; Schrock, R. R.; Reiff, W. M. Inorg. Chem. 1999, 38, 243-252. (15) O’Donoghue, M. B.; Zanetti, N. C.; Davis, W. M.; Schrock, R. R. J. Am. Chem. Soc. 1997, 119, 2753-2754. (16) Schrock, R. R.; Kolodziej, R. M.; Liu, A. H.; Davis, W. M.; Vale, M. G. J. Am. Chem. Soc. 1990, 112, 4338-4345. (17) Cradwick, P. D.; Chatt, J.; Crabtree, R. H.; Richards, R. L. J. Chem. Soc., Chem. Commun. 1975, 351-352. (18) Mercer, M. J. Chem. Soc., Dalton Trans. 1974, 1637-1640. (19) Mercer, M.; Crabtree, R. H.; Richards, R. L. J. Chem. Soc., Chem. Commum. 1973, 808-809. (20) Ishino, H.; Ishii, Y.; Hidai, M. Chem. Lett. 1998, 677-678.

10.1021/om000684j CCC: $20.00 © 2001 American Chemical Society Publication on Web 12/02/2000

Heterobimetallic Bridging Dinitrogen Complexes

Organometallics, Vol. 20, No. 1, 2001 189

Al,21 Ga22) compounds but also group 4 metal (Ti, Zr, Hf) complexes23 to afford the µ-N2 complexes. Treatment of 1 with [Cp2TiCl2] (Cp ) η5-C5H5) or [Cp2MCl2]/NaI (M ) Zr, Hf) affords the heterobimetallic bridging dinitrogen complexes [WX(PMe2Ph)4(µ-N2)MCp2Cl] (3a, M ) Ti, X ) Cl; 3b, M ) Zr, X ) I; 3c, M ) Hf, X ) I) in good yield. We have now extended this study to the reactions of complexes 1 and 2 with other group 4 and 5 transition metal complexes. Here we describe synthesis, characterization, and some reactivities of a series of heterobimetallic dinitrogen complexes in which the µ-N2 ligand bridges group 6 and group 4 or 5 metal centers. Results and Discussion Synthesis of Group 4-Group 6 Heterobimetallic Bridging Dinitrogen Complexes. In the previous communication,23 we reported that [Cp2TiCl2] shows moderate reactivity toward complex 1 at 50 °C to give the heterobimetallic bridging dinitrogen complex 3a in good yield. [Cp2MCl2] (M ) Zr, Hf) also reacts with 1 in the presence of NaI to form analogous µ-N2 complexes 3b and 3c. The crystallographically determined molecular structure of [WI(PMe2Ph)3(py)(µ-N2)ZrCp2Cl] (3b′, py ) pyridine) derived from 3b and pyridine revealed the linear W(µ-N2)Zr core with the formal (N2)2- ligand. To expand the scope of this synthetic method for heterobimetallic µ-N2 complexes, we turned our attention to the mono-Cp complex [CpTiCl3], which is expected to have higher reactivity toward dinitrogen complexes owing to its strong Lewis acidic nature. When complex 1 was allowed to react with an equimolar amount of [CpTiCl3] in benzene at room temperature, rapid reaction took place to form the heterodinuclear µ-N2 complex [WCl(PMe2Ph)4(µ-N2)TiCpCl2] (4), which was isolated in good yield after recrystallization (eq 1). The IR spectrum of 4 showed a medium absorption at

Figure 1. Molecular structures of 4 (A) and 9a‚3CH2Cl2 (B). Solvating CH2Cl2 molecules and hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level.

1408 cm-1 characteristic of the ν(NN) band, suggesting that the N-N bond has a double bond character, and 4 may be viewed as the formal (N2)2--bridged W(II)-Ti(IV) complex. It is to be noted that the ν(NN) value of complex 4 is considerably lower than that (1468 cm-1) of complex 3a.23 Substitution of the 15e- fragment TiCp2Cl in 3a with the 11e- fragment TiCpCl2 causes stronger π-donation from the N2 ligand to the titanium atom, which is reflected in the lower ν(NN) value. The 1H NMR and 31P NMR spectra showed a broad Me (21) Takahashi, T.; Kodama, T.; Watakabe, A.; Uchida, Y.; Hidai, M. J. Am. Chem. Soc. 1983, 105, 1680-1681. (22) Takagahara, K.; Ishino, H.; Ishii, Y.; Hidai, M. Chem. Lett. 1998, 897-898. (23) Mizobe, Y.; Yokobayashi, Y.; Oshita, H.; Takahashi, T.; Hidai, M. Organometallics 1994, 13, 3764-3766.

singlet at δ 1.63 and a singlet with 183W satellites (JWP ) 277 Hz) at δ -24.5, respectively, indicating the trans configuration of the chloride and µ-N2 ligands around the tungsten center. Attempted reactions of 1 with [Cp*TiCl3] (Cp* ) η5-C5Me5), [CpZrCl3], [Cp*ZrCl3], or [Cp*HfCl3] failed to give any isolable heterobimetallic µ-N2 complexes. The molecular structure of complex 4 was unambiguously determined by X-ray diffraction study (Figure 1). Selected bond distances and angles are collected in Table 1, and an ORTEP drawing is given in Figure 1. In accordance with the spectral data, complex 4 has an octahedral configuration around the tungsten center with the mutually trans µ-N2 and chloride ligands, and the titanium center adopts a typical three-legged piano

190

Organometallics, Vol. 20, No. 1, 2001

Table 1. Selected Bond Distances and Angles in 4 and 9a‚3CH2Cl2 4 (X ) Cl(3))

9a‚3CH2Cl2 (X ) N(3))

W(1)-N(1) N(1)-N(2) Ti(1)-N(2) W(1)-P(1) W(1)-P(2) W(1)-P(3) W(1)-P(4) Ti(1)-Cl(1) Ti(1)-Cl(2)

Distances (Å) 1.782(5) 1.270(8) 1.792(5) 2.525(6) 2.523(5) 2.513(6) 2.509(5) 2.313(3) 2.317(3)

1.85(1) 1.21(2) 1.82(1) 2.483(4) 2.489(5) 2.533(4) 2.516(5) 2.299(6) 2.307(6)

W(1)-N(1)-N(2) X-W(1)-N(1) Ti(1)-N(2)-N(1) P(1)-W(1)-N(1) P(2)-W(1)-N(1) P(3)-W(1)-N(1) P(4)-W(1)-N(1)

Angles (deg) 166(1) 176.8(5) 168.8(8) 97.7(5) 86.4(5) 94.4(5) 88.9(5)

178(1) 178.4(6) 179(1) 88.4(4) 87.2(4) 97.4(4) 100.7(4)

stool structure. The W-N-N-Ti array in 4 is almost linear, and this type of linear structure is ubiquitous in dinuclear µ-N2 complexes.2,24 The core structure is closely related to that of the previously reported W-Zr complex 3b′.23 The Ti-N distance at 1.792(5) Å is shorter than that found in the Mo-Ti µ-N2 complex [(PhtBuN)3Ti(µ-N2)Mo{NtBu(3,5-Me2C6H3)}3] (1.880(3) Å)11 but is in the range of Ti-N double bond distances found in titanium amido complexes such as [TiCl2{η5: η1-C5H4(CH2)3NiPr}] (1.867(2) Å),25 [Cp*Ti(NMe2)(CH2Ph)2] (1.887(2) Å),26 and [CpTiCl2(NPPh3)] (1.78(1) Å).27 The W-N distance at 1.782(5) Å also indicates a multiple-bonding character as found in complex 3b′. The N-N bond distance of 1.270(8) Å is slightly longer than those of the above-mentioned Mo-Ti complex (1.229(4) Å) and 3b′ (1.24(2) Å), and the N2 fragment in 4 may be viewed as a formal (N2)2- ligand which acts as a fourelectron donor to each of the tungsten and titanium centers. Although the dinitrogen complexes with dppe ligands 2 are unreactive toward [Cp2TiCl2], they react smoothly with [CpTiCl3]. Thus, when the tungsten complex 2a was treated with an equimolar amount of [CpTiCl3] at room temperature, [WCl(dppe)2(µ-N2)TiCpCl2] (5a), the dppe analogue of 4, was isolated in good yield. The spectral data of 5a including the IR absorption at 1412 cm-1 attributable to the ν(NN) vibration are consistent with the formulation. The 1H NMR signal of the Cp ligand appeared in the high-field region (δ 5.70) compared with those of 3a (δ 6.30) and 4 (δ 6.44), which is accounted for by the shielding effect of a phenyl group of the dppe ligands located nearby (vide infra). The molybdenum dinitrogen complex 2b similarly reacted with [CpTiCl3] to give the analogous Mo-Ti complex [MoCl(dppe)2(µ-N2)TiCpCl2] (5b). Complex [Cp2Ti(OTf)2] (OTf ) OSO2CF3) was also effective for the synthesis of µ-N2 W-Ti complexes from either 1 or 2a, and [W(OTf)(PMe2Ph)4(µ-N2)TiCp2(OTf)] (6a) or [W(OTf)(dppe)2(µ-N2)TiCp2(OTf)] (6b) was ob(24) Henderson, R. A. Transition Met. Chem. 1990, 15, 330-336. (25) Sinnema, P.-J.; Veen, L.; Spek, A. L.; Veldman, N.; Teuben, J. H. Organometallics 1997, 16, 4245-4247. (26) Sinnema, P.-J.; Spaniol, T. P.; Okuda, J. J. Organomet. Chem. 2000, 598, 179-181. (27) Latham, I. A.; Leigh, G. J.; Huttner, G.; Jibril, I. J. Chem. Soc., Dalton Trans. 1986, 377-383.

Ishino et al.

tained, respectively. The low electroconductivitiy of 6a and 6b (6.6 S cm2 mol-1 for 6a and 6.9 S cm2 mol-1 for 6b in CH2Cl2) implies that they are essentially nonelectrolytes with coordinated OTf ligands. It should be noted that treatment of chloro complexes such as 3a or 5a with AgOTf failed to give the corresponding OTf derivatives. The anionic dinitrogen complex trans-[NBu4][W(NCS)(N2)(dppe)2] (7) readily derived from complex 2a shows higher reactivities toward electorophiles than 2a, which is substantiated in the reactions with fluoroarene complexes.28,29 As expected, complex 7 smoothly reacted with [Cp2MCl2] (M ) Ti, Zr, Hf) and [Cp′TiCl3] (Cp′ ) Cp, Cp*) at room temperature to give [W(NCS)(dppe)2(µ-N2)MCp2Cl] (8a, M ) Ti; 8b, M ) Zr; 8c, M ) Hf) and [W(NCS)(dppe)2(µ-N2)TiCp′Cl2] (9a, Cp′ ) Cp; 9b, Cp′ ) Cp*), respectively (eq 2). The IR spectra of 8a-c

showed strong absorptions at 2049-2056 cm-1 and medium absorptions at 1545-1559 cm-1 attributable to the ν(NCS) and ν(NN) bands, respectively, while the ν(NN) values for 9a (1441 cm-1) and 9b (1433 cm-1) were considerably lower (vide supra). The 1H NMR and 31P NMR spectra also agreed well with the formulation. The molecular structure of 9a‚3CH2Cl2 was confirmed crystallographically. As shown in Figure 1, the structure around the dinuclear core of 9a is closely related to that of 4 except that the W(1)-N(1) and Ti(1)-N(2) bonds in 9a are slightly elongated, while the N(1)-N(2) bond distance is shorter than that in 4. The CpTi moiety is situated in the vicinity of one of the dppe phenyl rings (28) Ishii, Y.; Kawaguchi, M.; Ishino, Y.; Aoki, T.; Hidai, M. Organometallics 1994, 13, 5062-5071. (29) Ishii, Y.; Ishino, Y.; Aoki, T.; Hidai, M. J. Am. Chem. Soc. 1992, 114, 5429-5430.

Heterobimetallic Bridging Dinitrogen Complexes

Organometallics, Vol. 20, No. 1, 2001 191

Table 2. Selected Bond Distances and Angles in 10a‚CH2Cl2‚Et2O and 10d‚2MeCN 10a‚CH2Cl2‚Et2O (M ) Nb)

10d‚2MeCN (M ) Ta)

W(1)-N(1) N(1)-N(2) M(1)-N(2) M(1)-Cl(1) M(1)-Cl(2) M(1)-Cl(3)

Distances (Å) 1.785(7) 1.254(9) 1.852(7) 2.492(3) 2.434(3) 2.481(3)

1.783(7) 1.275(9) 1.857(8) 2.462(3) 2.446(3) 2.449(3)

W(1)-N(1)-N(2) Cl(4)-W(1)-N(1) M(1)-N(2)-N(1)

Angles (deg) 176.0(6) 176.4(2) 179.1(6)

173.5(6) 173.5(6) 174.2(7)

(C(21)-C(26)). Such conformation is required to accommodate the bulky CpTi group and explains the observation that the Cp protons of the µ-N2 complexes with dppe ligands resonate in a higher field region (δ 5.6-5.9) than those of the PMe2Ph analogues (δ 6.1-6.5). In contrast with the above reactions, [Cp*ZrCl3] did not react with complex 7, and [CpZrCl3] or [Cp*HfCl3] gave the W(I) dinitrogen complex trans-[W(NCS)(dppe)2(N2)]30 as the only characterized product. Synthesis of Group 5-Group 6 Heterobimetallic Bridging Dinitrogen Complexes. Synthesis of a series of W-Nb and W-Ta µ-N2 complexes was also examined to compare the reactivities of the group 4-group 6 and group 5-group 6 heterobimetallic µ-N2 complexes. When complex 1 was allowed to react with [Cp′MCl4] (M ) Nb, Ta; Cp′ ) Cp, Cp*) in benzene at room temperature, the µ-N2 complexes [WCl(PMe2Ph)4(µ-N2)MCp′Cl3] (10a, M ) Nb, Cp′ ) Cp; 10b, M ) Nb, Cp′ ) Cp*; 10c, M ) Ta, Cp′ ) Cp; 10d, M ) Ta, Cp′ ) Cp*) were formed in high yield (eq 3). The 1H NMR

spectra of 10a-d showed a broad singlet assignable to the PMe protons, and the 31P{1H} NMR spectra exhibited a singlet with 183W satellites. In the IR spectra, medium absorptions attributable to the ν(NN) band were observed at 1385-1435 cm-1, where the ν(NN) values of the W-Nb complexes 10a and 10b are lower than those of the W-Ta analogues 10c and 10d by ca. 40 cm-1. The molecular structures of complex 10a‚CH2Cl2‚Et2O and 10d‚2MeCN were unambiguously determined by X-ray diffraction study. Selected bond distances and angles are listed in Table 2, and their ORTEP drawings (30) Chatt, J.; Leigh, G. J.; Neukomm, H.; Pickett, C. J.; Stanley, D. R. J. Chem. Soc., Dalton Trans. 1980, 121-127.

Figure 2. Molecular structures of 10a‚CH2Cl2‚Et2O (A) and 10d‚2MeCN (B). Solvating ether and MeCN molecules and hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level.

are depicted in Figure 2. In agreement with the spectral data, the tungsten centers in 10a and 10d have an octahedral configuration with the mutually trans µ-N2 and chloro ligands, and the niobium and tantalum centers take a square pyramidal geometry with the Cp′ ligand at the apex. The W-N-N-Nb and W-N-NTa arrays are almost linear, as observed in 3b′, 4, and 9a‚3CH2Cl2. The N-N bond distances (1.254(9) Å for 10a‚CH2Cl2‚Et2O and 1.275(9) Å for 10d‚2MeCN) are

192 Organometallics, Vol. 20, No. 1, 2001

Figure 3. Molecular structure of 11a‚Et2O. Solvating ether molecule and hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. Selected bond distances (Å) and angles (deg): W(1)-N(1), 1.806(8); N(1)-N(2), 1.25(1); Nb(1)-N(2), 1.868(9); 2.467(4); W(1)-N(1)-N(2), 171.1(8); Nb(1)-N(2)-N(1), 175.0(8).

close to that of 4 and correspond to the bond order of 2. Thus, the oxidation state of the diamagnetic metal centers in these complexes may be assigned to be W(II)M(V) (M ) Nb, Ta). Crystallographically characterized heterobimetallic dinitrogen complexes containing group 5 metals have not been known until very recently. The Mo-V and Mo-Nb complexes [{[(Me3SiNCH2CH2)3N]Mo(µ-N2)}2VCl(THF)] (N-N, 1.217(7) and 1.221(7) Å)14 and [{(3,5-Me2C6H3)tBuN}3Mo(µ-N2)Nb{NiPr(C6H3Me23,5)}3] (N-N, 1.235(10) Å)13 have been considered as formal (N2)2- complexes, and their N-N distances are compared well with those found for 10a and 10d. Complexes 2a and 7 also gave analogous µ-N2 complexes [WCl(dppe)2(µ-N2)MCpCl3] (11a, M ) Nb; 11b, M ) Ta) and [W(NCS)(dppe)2(µ-N2)MCpCl3] (12a, M ) Nb; 12b, M ) Ta) in good yield on reactions with [CpMCl4] (M ) Nb, Ta). However, they failed to react with [Cp*MCl4] probably due to steric reasons. The molecular structure of 11a‚Et2O established by crystallographic study is given in Figure 3. The structure around the dinuclear core is closely related to that of 10a. Reactions of the Heterobimetallic Dinitrogen Complexes with Unsaturated Compounds. Metalnitrogen multiple bonds have been known to undergo interesting reactions with unsaturated compounds including the [2+2] cycloaddition to form a metallacycle.31-33 Aiming at developing new coupling reactions of the µ-N2 ligand and organic unsaturated compounds, reactions of complexes 4, 5a, 6a, 10a, 10d, 11a, and 11b with various alkenes, alkynes, CO, and isocyanides were (31) Blake, R. E.; Antonelli, D. M.; Henling, L. M.; Schaefer, W. P.; Hardcastle, K. I.; Bercaw, J. E. Organometallics 1998, 17, 718-725. (32) Fairfax, D.; Stein, M.; Livinghouse, T.; Jensen, M. Organometallics 1997, 16, 1523-1525. (33) Walsh, P. J.; Hollander, F. J.; Bergman, R. G. Organometallics 1993, 12, 3705-3723.

Ishino et al.

examined. Unfortunately, however, most of the attempted reactions yielded a complex mixture of uncharacterized products. Only in the reaction of 10d with tBuNC (5 equiv) at 50 °C did substitution of one PMe 2 Ph ligand on the tungsten atom take place to form [WCl (PMe2Ph)3(tBuNC)(µ-N2)TaCp*Cl3] (13) in moderate yield. Complex 13 showed a ν(CN) absorption at 2112 cm-1 as well as a ν(NN) absorption at 1458 cm-1, and the 1H and 31P{1H} NMR data suggest the mer arrangement of the PMe2Ph ligands. It should also be mentioned that complex 10d did not undergo ligand substitution with pyridine or 2,2′-bipyridine, although one of the PMe2Ph ligands in the W-Zr complex 3b was readily displaced by pyridine to give 3b′. Synthesis of Bridging Dinitrogen Complexes with Alkyl Ligands. Attempts to introduce methyl ligands to the dinuclear cores of the µ-N2 complexes 4, 5a, 6a, 9a, 10a, 10c, 11a, or 11b by reactions with MeLi or MeMgBr resulted in the reduction of the tungsten center to give the parent dinitrogen complexes 1 and 2a as the only characterizable product. Use of other alkylmetals such as Me2Zn and Me4Sn was not successful either. However, several µ-N2 complexes with alkyl ligands were obtained through the reaction of the dinitrogen complexes 1, 2, and 7 with [Cp2ZrMeCl], [Me3TaCl2], or [Me2NbCl3]. Although the reaction of 1 with [Cp2ZrMeCl] did not proceed in the absence of NaI, addition of excess NaI effectively promoted the reaction to give the µ-N2 complex [WI(PMe2Ph)4(µ-N2)ZrCp2Me] (14a). The IR spectrum of 14a showed a medium ν(NN) band at 1541 cm-1, and the Me signal in its 1H NMR appeared as a singlet at δ 0.37. In contrast with the reaction of 1, the anionic dinitrogen complex 7 reacted with [Cp2ZrMeCl] in the absence of NaI to form [W(NCS)(dppe)2(µ-N2)ZrCp2Me] (14b). This complex exhibited a singlet at δ -0.02 in the 1H NMR spectrum attributable to the Zr-Me group. The molecular structure of 14b confirmed by crystallographic study is shown in Figure 4. The Zr(1)C(1) distance at 2.342(8) Å is not unusual, and other metrical features are similar to those observed in 3b′. On the other hand, treatment of 1 and 2 with [Me3TaCl2] afforded [WCl(PMe2Ph)4(µ-N2)TaMe3Cl] (15a) and [MCl(dppe)2(µ-N2)TaMe3Cl] (15b, M ) W; 15c, M ) Mo), respectively, in moderate yield. In the 1H NMR spectra, the Me signals of these complexes were observed as a singlet at δ 0.45, 0.23, and 0.13, respectively, and the spectrum of 15b showed essentially no temperature dependence over the range 20 to -60 °C. A structure having a trigonal bipyramidal tantalum center with the chloro and µ-N2 ligands at the apical positions is consistent with the spectral data, but we must await further investigation to clarify the detailed structure of 15. Similarly, complexes 2 reacted with [Me2NbCl3] to produce [MCl(dppe)2(µ-N2)NbMe2Cl2] (16a, M ) W; 16b, M ) Mo). Complexes 14-16 are thermally stable up to 70 °C, and migration of the Me group from the metal to the µ-N2 ligand has not been observed so far. Reaction of the Heterobimetallic Dinitrogen Complexes with Li2S5. In relevalence to the active site of nitrogenase, great interest has been focused on multimetallic dinitrogen complexes having sulfur-based ligands, although examples of such complexes are still

Heterobimetallic Bridging Dinitrogen Complexes

Organometallics, Vol. 20, No. 1, 2001 193 Table 3. Selected Bond Distances and Angles in 17‚1.5Et2O W(1)-N(1) Ti(1)-N(2) Ti(1)-S(5) S(2)-S(3) S(4)-S(5) W(1)-N(1)-N(2) Ti(1)-N(2)-N(1) S(5)-Ti(1)-N(2) Ti(1)-S(5)-S(4) S(2)-S(3)-S(4)

Distances (Å) 1.799(8) N(1)-N(2) 1.827(9) Ti(1)-S(1) 2.374(4) S(1)-S(2) 2.033(6) S(3)-S(4) 2.053(5) Angles (deg) 176.5(7) Cl(1)-W(1)-N(1) 172.6(7) S(1)-Ti(1)-N(2) 98.2(3) Ti(1)-S(1)-S(2) 100.4(2) S(1)-S(2)-S(3) 106.5(2) S(3)-S(4)-S(5)

1.247(9) 2.406(4) 2.055(5) 2.050(6)

177.1(3) 97.1(3) 102.1(2) 105.8(2) 105.1(2)

Figure 4. Molecular structure of 14b. Hydrogen atoms except for the Zr-CH3 hydrogens are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. Selected bond distances (Å) and angles (deg): W(1)-N(1), 1.850(5); N(1)-N(2), 1.223(7); Zr(1)-N(2), 2.042(6); Zr(1)C(1), 2.342(8); W(1)-N(1)-N(2), 173.6(5); Zr(1)-N(2)-N(1), 174.6(5); C(1)-Zr(2)-N(2), 98.4(3).

limited.34-36 Having a series of heterobimetallic µ-N2 complexes in hand, we next investigated their reactions with sulfur ligands. When complex 5a was treated with Li2S5 in THF at room temperature, the µ-N2 complex with the pentasulfido ligand [WCl(dppe)2(µ-N2)TiCpS5] (17) was isolated in good yield (eq 4). However, atFigure 5. Molecular structures of 17‚1.5Et2O. Solvating ether molecules and hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level.

tempted reactions of 4, 10a, or 11a with Li2S5 and of 5a with Li2S, Li2S2, or [NH4]2[WS4] led to uncharacterized mixtures. The 1H and 31P NMR spectra of 17 were comparable to those of 5a, and the IR spectrum of 17 showed a medium ν(NN) absorption at 1406 cm-1, which is slightly lower than that of 5a. These spectral data indicate that the core structure of 5a was maintained during the reaction with Li2S5. (34) O’Regan, M. B.; Liu, A. H.; Finch, W. C.; Schrock, R. R.; Davis, W. M. J. Am. Chem. Soc. 1990, 112, 4331-4338. (35) Henderson, R. A.; Morgan, S. H. J. Chem. Soc., Dalton Trans. 1990, 1107-1109. (36) Schrock, R. R.; Wesolek, M.; Liu, A. H.; Wallace, K. C.; Dewan, J. C. Inorg. Chem. 1988, 27, 2050-2054.

The molecular structure of complex 17‚1.5Et2O was confirmed by an X-ray diffraction study. Selected bond distances and angles are summarized in Table 3, and an ORTEP drawing is given in Figure 5. In agreement with the spectral data, complex 17 has a linear W-NN-Ti core with the N-N bond distance at 1.247(9) Å. The η2-pentasulfido ligand is bonded to the Ti atom to form a six-membered ring with the chair conformation, and the CpTiS5 fragment takes the structure that minimizes the steric congestion with the dppe ligands on the tungsten atom. The distances of the Ti-S (2.406(4), 2.374(4) Å) and S-S (2.033(6)-2.055(5) Å) bonds are comparable with those found in other titanium polysulfido complexes including [Cp2TiS5].37,38 Investigation into the reactivity of 17 is now in progress. Protonation of Heterobimetallic Dinitrogen Complexes with H2SO4. The protonation of coordinated dinitrogen to form NH3 or NH2NH2 requires the concomitant transfer of six or four electrons, respectively, from the metal center. Therefore, as far as mononuclear (37) Mu¨ller, E. G.; Petersen, J. L.; Dahl, L. F. J. Organomet. Chem. 1976, 111, 91-112. (38) Epstein, E. F.; Bernal, I. J. Organomet. Chem. 1971, 26, 229245.

194

Organometallics, Vol. 20, No. 1, 2001

Ishino et al.

Table 4. Protonation of Bridging Dinitrogen Ligands Forming Ammonia and/or Hydrazinea complex

yield of NH3 (%)a

yield of NH2NH2 (%)a

3ab

43 17 36 44 34 29 41 23

8 16 2 6 2 9 0 10

3bb 4 10a 10b 10c 10d 15a a

Based on total nitrogen in the N2 complex. Reaction conditions: heterobimetalic dinitrogen complex (0.050-0.100 mmol); H2SO4 (10 equiv); MeOH (3 mL); room temperature; 3 h; under Ar. b See ref 23.

dinitrogen complexes are concerned, such conversion is expected to occur effectively only with complexes of highly electron-rich metal centers such as complex 1, where all the electrons are provided from the single metal. On the other hand, the conversion of coordinated dinitrogen to nitrogen hydrides on multimetallic complexes is presumed to require less electrons per one metal atom, and more diversified metals are expected to effect such reactions. In fact, it has been demonstrated that various types of multinuclear dinitrogen complexes yield NH3 and NH2NH2 on protonolysis under mild conditions.2 To gain information about the chemical properties of dinitrogen activated by the group 4 or 5-group 6 metal pairs, we have investigated the protonation reactions with H2SO4. Representative results are summarized in Table 4 together with the values for 3a and 3b reported previously.23 As observed with 3a and 3b, the heterobimetallic µ-N2 complexes with PMe2Ph ligands, 4, 10a-d, and 15a, gave NH3 in 23-44% yield, while NH2NH2 was formed in lower yield (0-10%). Essentially no N2 gas evolution was observed. Unfortunately, we could not characterize the metal products, and the fate of nitrogen is not fully understood. On the other hand, complexes having dppe ligands (5a, 5b, 8b, 8c, 11a, and 11b) gave much lower yields of NH3 (0-6%) and NH2NH2 (0-1%), and considerable amounts of the starting complexes were recovered. It should be pointed out that NH2NH2 is most commonly observed as the major nitrogen hydride product in the protonation of homobimetallic µ-N2 complexes.2 In addition, protonolysis of heterodinuclear µ-N2 complexes has not been studied extensively. It has been reported that treatment of the W-Ta complex [Cp*WMe3(µ-N2)TaCp*Me2] with HOTf gives the mononuclear tungsten hydrazido(1-) complex [Cp*Me3W(η2-NHNH2)][OTf] and [Cp*TaMe2(OTf)2],39 while the hydrolysis of the Re-Cr complex [ReCl(PMe2Ph)4(µ-N2)CrCl3(THF)2] results in the formation of [ReCl(N2)(PMe2Ph)4].40 In contrast, the reaction of the Mo-W µ-N2 complex [Cp*MoMe3(µ-N2)WCp*Me3] with HCl affords NH3 in 16% yield based on the total nitrogen.16 In the protonation reactions of the heterobimetallic µ-N2 complexes derived from 1, the group 4 or 5 fragment seems to have minor effects on the NH3/ NH2NH2 selectivity, although the mechanism of the protonation and N-N bond cleavage at the dinuclear cores is still unclear. (39) Glassman, T. E.; Liu, A. H.; Schrock, R. R. Inorg. Chem. 1991, 30, 4723-4732. (40) Chatt, J.; Fay, R. C.; Richards, R. L. J. Chem. Soc., A 1971, 702.

Finally, reduction of the µ-N2 complexes 4, 5a, 10a, and 10b with sodium or magnesium was also examined, since the conversion of µ-N2 complexes to the corresponding nitrides in the presence9,10,11,13 or absence41-43 of alkali metals has recently been established. However the only characterized products were the parent dinitrogen complexes 1 and 2a. Concluding Remarks We have succeeded in the systematic synthesis of a series of heterobimetallic dinitrogen complexes containing group 6 and group 4 or 5 transition metals. The synthetic method established in this study provides an important approach to the chemistry of dinitrogen activated by two different metal centers, which still remains much less developed in comparison with the chemistry of homodinuclear dinitrogen complexes. The spectroscopic and structural properties of the µ-N2 complexes newly prepared were examined in detail, revealing that the µ-N2 moiety is best regarded as a formal (N2)2- ligand. Protonation of the coordinated dinitrogen in these complexes gave rise to the formation of ammonia and hydrazine, whereas migration of a Me group from the group 4 or 5 metal center to the dinitrogen ligand has not been observed. The lability of the chloro ligands on the titanium atom in 5a also enabled us to obtain the sulfur-rich bridging dinitrogen complex 17, which is a rare example of µ-N2 complexes with sulfur donor ligands and is interesting in relevalence to the metal-sulfur multinuclear structure in the active site of nitrogenase. Further study on the chemical transformation of the µ-N2 ligand in the group 6-group 4 or 5 heterodinuclear complexes is under way. Experimental Section General Procedure. All reactions were carried out under a dry nitrogen atmosphere unless otherwise noted. Solvents were dried by usual methods and distilled before use. Li2S544 and complexes 1,45 2a,45 2b,46 7,30 [Cp2ZrMeCl],47 [Cp*NbCl4],48 [CpTaCl4],49 [Me3TaCl2],50 and [Me2NbCl3]51 were prepared according to the literature methods. Other reagents were commercially obtained and used without further purification. 1H and 31P{1H} NMR spectra were recorded on a JEOL JNM-EX-270 (1H, 270 MHz; 31P, 109 MHz) or JEOL JNM-LA400 (1H, 400 MHz; 31P, 162 MHz) spectrometer. IR spectra were recorded on a Shimadzu FTIR-8100M spectrophotometer. Quantitative GLC analyses were carried out on a Shimadzu GC-8A instrument equipped with a thermal conductivity (41) Cummins, C. C. Chem. Commun. 1998, 1777-1786. (42) Laplaza, C. E.; Johnson, M. J. A.; Peters, J. C.; Odom, A. L.; Kim, E.; Cummins, C. C.; George, G. N.; Pickering, I. J. J. Am. Chem. Soc. 1996, 118, 8623-8638. (43) Laplaza, C. E.; Johnson, A. R.; Cummins, C. C. J. Am. Chem. Soc. 1996, 118, 709-710. (44) Shaver, A.; Mccall, J. M.; Marmolejo, G. Inorg. Synth. 1990, 27, 59-65. (45) Chatt, J.; Heath, G. A.; Richards, R. L. J. Chem. Soc., Dalton Trans. 1974, 2074-2082. (46) Dilworth, J. R.; Richards, R. L.; Chen, G. J.-J.; MacDonald, J. W. Inorg. Synth. 1980, 20, 119-127. (47) Jordan, R. F. J. Organomet. Chem. 1985, 294, 321-326. (48) Okamoto, T.; Yasuda, H.; Nakamura, A.; Kai, Y.; Kanehisa, N.; Kasai, N. J. Am. Chem. Soc. 1988, 110, 5008-5017. (49) Cardoso, A. M.; Clark, R. J. H.; Moorhouse, S. J. Chem. Soc., Dalton Trans. 1980, 1156-1160. (50) Schrock, R. R.; Sharp, P. R. J. Am. Chem. Soc. 1978, 100, 23892399. (51) Fowles, G. W. A.; Rice, D. A.; Winkins, J. D. J. Chem. Soc., Dalton Trans. 1972, 2313-2318.

Heterobimetallic Bridging Dinitrogen Complexes detector using a Molecular Sieve 13X column. Elemental analyses were performed with a Perkin-Elmer 2400 series II CHN analyzer. Preparation of [WCl(PMe2Ph)4(µ-N2)TiCp2Cl] (3a). Complex 1 (500.0 mg, 0.631 mmol) and [Cp2TiCl2] (157.0 mg, 0.631 mmol) were dissolved in benzene (12.5 mL) at room temperature, and the mixture was stirred for 17 h at 50 °C. Then the solution was concentrated to ca. 6 mL under vacuum at room temperature. Layering the benzene solution with hexane afforded 3a as a black solid, which was collected, washed with hexane, and dried in vacuo (466.0 mg, 73% yield): 1H NMR (C6D6) δ 1.57 (s, 24H, PMe), 6.30 (s, 10H, Cp), 6.98-7.54 (m, 20H, Ph); IR (KBr) 1468 (m) cm-1. Anal. Calcd for C42H54Cl2N2P4TiW: C, 49.78; H, 5.37; N, 2.76. Found: C, 49.40; H, 5.61; N, 2.53. Preparation of [WI(PMe2Ph)4(µ-N2)ZrCp2Cl]‚0.5C6H6 (3b‚0.5C6H6), [WI(PMe2Ph)3(py)(µ-N2)ZrCp2Cl]‚0.5py (3b′‚ 0.5py), and [WI(PMe2Ph)4(µ-N2)HfCp2Cl]‚C6H6 (3c‚C6H6). Complex 1 (200.0 mg, 0.252 mmol), [Cp2ZrCl2] (73.8 mg, 0.252 mmol), and NaI (550.0 mg, 3.70 mmol) were dissolved in benzene (5 mL) at room temperature, and the mixture was stirred for 16 h at 50 °C under dark. Then the solution was cooled to room temperature and filtered. Layering the filtered solution with hexane afforded 3b‚0.5C6H6 as a dark red solid, which was collected, washed with hexane, and dried in vacuo (192.0 mg, 64% yield): 1H NMR (C6D6) δ 1.71 (s, 24H, PMe), 6.33 (s, 10H, Cp), 6.98-7.48 (m, 20H, Ph); IR (KBr) 1518 (m) cm-1. Anal. Calcd for C45H57ClIN2P4WZr: C, 45.52; H, 4.84; N, 2.36. Found: C, 45.59; H, 4.89; N, 2.22. The pyridine complex [WI(PMe2Ph)3(py)(µ-N2)ZrCp2Cl]‚ 0.5py (3b′‚0.5py) was obtained in 44% yield by dissolving complex 3b‚0.5C6H6 in pyridine followed by addition of hexane to the pyridine solution and further recrystallization of the solid deposited from toluene-pyridine/hexane. 1H NMR (C4D8O): δ 1.50 (t, 6H, J ) 2.7 Hz, trans PMe), 1.59 (t, 6H, J ) 2.7 Hz, trans PMe), 1.90 (d, 6H, J ) 6.0 Hz, unique PMe), 6.24 (s, 10H, Cp), 6.82-7.41 (m, 15H, Ph). This complex is somewhat unstable in solution, and signals of the pyridine ligand were obscured by overlapping with those of decomposition products. IR (KBr): 1541 (m) cm-1. Anal. Calcd for C41.5H50.5ClIN3.5P3WZr: C, 44.16; H, 4.51; N, 4.34. Found: C, 44.62; H, 4.56; N, 4.30. Complex 3c‚C6H6 was prepared from 1, [Cp2HfCl2], and NaI as a brown solid in 60% yield by a procedure similar to that described for complex 3b‚0.5C6H6. 1H NMR (C6D6): δ 1.77 (s, 24H, PMe), 6.29 (s, 10H, Cp), 6.99-7.70 (m, 20H, Ph); IR (KBr) 1545 (m) cm-1. Anal. Calcd for C48H66ClHfIN2P4W: C, 43.89; H, 4.60; N, 2.13. Found: C, 43.85; H, 4.63; N, 2.08. Preparation of [WCl(PMe2Ph)4(µ-N2)TiCpCl2] (4). Complex 1 (225.2 mg, 0.284 mmol) and [CpTiCl3] (62.2 mg, 0.284 mmol) were dissolved in benzene (5 mL) at room temperature. With rapid evolution of nitrogen gas, the color of the solution immediately changed from orange to dark green. The mixture was stirred for a further 8 h, and the solvent was evaporated under vacuum to give a dark green solid. The residual solid was dissolved in CH2Cl2, and the solution was filtered. Layering the CH2Cl2 solution with ether afforded black crystals of 4, which were collected, washed with ether, and dried in vacuo (196.0 mg, 70% yield): 1H NMR (CDCl3) δ 1.63 (s, 24H, PMe), 6.44 (s, 5H, Cp), 7.27-7.46 (m, 20H, Ph); 31P{1H} NMR (CDCl3) δ -24.5 (s with 183W satellites, JWP ) 277 Hz); IR (KBr) 1408 (m) cm-1. Anal. Calcd for C37H49Cl3N2P4TiW: C, 45.17; H, 5.02; N, 2.85. Found: C, 45.50; H, 5.29; N, 2.70. Preparation of [WCl(dppe)2(µ-N2)TiCpCl2]‚CH2Cl2‚ Et2O (5a‚CH2Cl2‚Et2O) and [MoCl(dppe)2(µ-N2)TiCpCl2] (5b). Complex 2a (198.0 mg, 0.191 mmol) and [CpTiCl3] (41.9 mg, 0.191 mmol) were dissolved in THF (5 mL) at room temperature. With rapid evolution of nitrogen gas, the color of the solution changed from orange to dark green. The mixture was stirred for a further 8 h, and the solvent was evaporated to give a dark green solid. The residual solid was dissolved in

Organometallics, Vol. 20, No. 1, 2001 195 CH2Cl2, and the solution was filtered. Layering the CH2Cl2 solution with ether afforded black crystals of 5a‚CH2Cl2‚Et2O, which were collected, washed with ether, and dried in vacuo (166.2 mg, 63% yield): 1H NMR (CDCl3) δ 2.46, 2.89 (br, 4H each, CH2 of dppe), 5.70 (s, 5H, Cp), 6.66-7.67 (m, 40H, Ph); 31 P{1H} NMR (CDCl3) δ 36.0 (s with 183W satellites, JWP ) 284 Hz); IR (KBr) 1412 (m) cm-1. Anal. Calcd for C62H65Cl5N2OP4TiW: C, 53.69; H, 4.72; N, 2.02. Found: C, 53.49; H, 4.60; N, 2.19. Complex 5b was prepared from 2b and [CpTiCl3] as black crystals in 78% yield by a procedure similar to that described for complex 5a‚CH2Cl2‚Et2O: 1H NMR (CDCl3) δ 2.31, 2.66 (br, 4H each, CH2 of dppe), 5.73 (s, 5H, Cp), 6.78-7.77 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 52.9 (s); IR (KBr) 1416 (m) cm-1. Anal. Calcd for C57H53Cl3MoN2P4Ti: C, 60.05; H, 4.69; N, 2.46. Found: C, 60.13; H, 5.06; N, 2.22. Preparation of [W(OTf)(PMe2Ph)4(µ-N2)TiCp2(OTf)] (6a). Complex 1 (120.1 mg, 0.152 mmol) and [Cp2Ti(OTf)2] (72.2 mg, 0.152 mmol) were dissolved in benzene (3 mL) at room temperature. With rapid evolution of nitrogen gas, the color of the solution immediately changed from orange to black. The mixture was stirred for further 30 min and filtered. Addition of hexane to the filtrate afforded 6a as a brown solid (181.3 mg, 96% yield): 1H NMR (C6D6) δ 1.51 (s, 24H, PMe), 6.21 (s, 10H, Cp), 6.98-7.23 (m, 20H, Ph); 31P{1H} NMR (C6D6) δ -25.4 (s with 183W satellites, JWP ) 290 Hz); IR (KBr) 1555 (m) cm-1. Anal. Calcd for C44H54F6N2O6P4S2TiW: C, 42.60; H, 4.39; N, 2.26. Found: C, 42.90; H, 4.59; N, 2.23. Preparation of [W(OTf)(dppe)2(µ-N2)TiCp2(OTf)] (6b). Complex 2a (172.0 mg, 0.166 mmol) and [Cp2Ti(OTf)2] (79.0 mg, 0.166 mmol) were dissolved in benzene (3 mL) at room temperature. With rapid evolution of nitrogen gas, the color of the solution changed from orange to black, and a black solid began to precipitate. The suspension was stirred for further 30 min, and the solvent was evaporated under vacuum to give a black solid. The residual solid was dissolved in THF, and the solution was filtered. Layering the THF solution with hexane afforded 6b as a brown solid (151.6 mg, 88% yield): 1H NMR (C D O) δ 2.60, 3.10 (br, 4H each, CH of dppe), 5.91 4 8 2 (s, 10H, Cp), 6.68-7.52 (m, 40H, Ph); 31P{1H} NMR (C4D8O) δ 41.4 (s with 183W satellites, JWP ) 297 Hz); IR (KBr) 1545 (m) cm-1. Anal. Calcd for C64H58F6N2O6P4S2TiW: C, 51.77; H, 3.94; N, 1.89. Found: C, 52.03; H, 4.33; N, 2.12. Preparation of [W(NCS)(dppe)2(µ-N2)TiCp2Cl]‚CH2Cl2 (8a‚CH2Cl2), [W(NCS)(dppe)2(µ-N2)ZrCp2Cl]‚CH2Cl2 (8b‚ CH2Cl2), and [W(NCS)(dppe)2(µ-N2)HfCp2Cl]‚0.5CH2Cl2 (8c‚0.5CH2Cl2). Complex 7 (110.4 mg, 0.084 mmol) and [Cp2TiCl2] (21.0 mg, 0.084 mmol) were dissolved in benzene (3 mL), and the mixture was stirred for 10 h at room temperature. During this period, the color of the solution gradually changed from black to dark red. Then the reaction mixture was evaporated under vacuum to give a black solid. The residual solid was dissolved in CH2Cl2, and the solution was filtered. Layering the CH2Cl2 solution with hexane afforded black crystals of 8a‚CH2Cl2, which were collected, washed with hexane, and dried in vacuo (71.0 mg, 62% yield): 1H NMR (CDCl3) δ 2.54, 2.95 (br, 4H each, CH2 of dppe), 5.65 (s, 10H, Cp), 6.44-7.55 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 37.9 (s with 183W satellites, JWP ) 288 Hz); IR (KBr) 2049 (s), 1545 (m) cm-1. Anal. Calcd for C64H60Cl3N3P4STiW: C, 56.31; H, 4.43; N, 3.08. Found: C, 56.01; H, 4.54; N, 2.75. The zirconium analogue 8b‚CH2Cl2 was prepared from 7 and [Cp2ZrCl2] by a procedure similar to that described for complex 8a‚CH2Cl2 and isolated as black crystals in 65% yield: 1H NMR (CDCl3) δ 2.41, 2.77 (br, 4H each, CH2 of dppe), 5.85 (s, 10H, Cp), 6.49-7.66 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 44.6 (s with 183W satellites, JWP ) 292 Hz); IR (KBr) 2056 (s), 1549 (m) cm-1. Anal. Calcd for C64H60Cl3N3P4SWZr: C, 54.57; H, 4.29; N, 2.98. Found: C, 54.17; H, 4.51; N, 2.92. The hafnium analogue 8c‚0.5CH2Cl2 was prepared similarly from 7 and [Cp2HfCl2] and isolated as black crystals in 66%

196

Organometallics, Vol. 20, No. 1, 2001

yield: 1H NMR (CDCl3) δ 2.17, 2.56 (br, 4H each, CH2 of dppe), 5.60 (s, 10H, Cp), 6.66-7.50 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 47.2 (s with 183W satellites, JWP ) 286 Hz); IR (KBr) 2056 (s), 1559 (m) cm-1. Anal. Calcd for C63.5H59Cl2HfN3P4SW: C, 52.48; H, 4.09; N, 2.89. Found: C, 52.44; H, 4.36; N, 2.55. Preparation of [W(NCS)(dppe)2(µ-N2)TiCpCl2]‚3CH2Cl2 (9a‚3CH2Cl2) and [W(NCS)(dppe)2(µ-N2)TiCp*Cl2] (9b). Complex 7 (109.7 mg, 0.084 mmol) and [CpTiCl3] (18.4 mg, 0.084 mmol) were dissolved in benzene (3 mL), and the mixture was stirred for 17 h at room temperature. The resulting reaction mixture was evaporated under vacuum to give a green solid. The residual solid was dissolved in CH2Cl2, and the solution was filtered. Layering the CH2Cl2 solution with ether afforded dark green crystals of 9a‚3CH2Cl2, which were collected, washed with ether, and dried in vacuo (68.0 mg, 54% yield): 1H NMR (CDCl3) δ 2.49, 2.81 (br, 4H each, CH2 of dppe), 5.80 (s, 5H, Cp), 6.55-7.63 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 38.2 (s with 183W satellites, JWP ) 284 Hz); IR (KBr) 2041 (s), 1441 (m) cm-1. Anal. Calcd for C61H59Cl8N3P4STiW: C, 48.67; H, 3.95; N, 2.79. Found: C, 49.02; H, 3.77; N, 2.88. Complex 9b was prepared from 7 and [Cp*TiCl3] as dark green crystals in 64% yield by a similar procedure except that 9b was isolated by recrystallization from ClCH2CH2Cl/hexane: 1H NMR (C6D6) δ 1.90 (s, 15H, Cp*), 2.19, 2.58 (br, 4H each, CH2 of dppe), 6.63-7.88 (m, 40H, Ph); 31P{1H} NMR (C6D6) δ 44.3 (s with 183W satellites, JWP ) 286 Hz); IR (KBr) 2041 (s), 1433 (m) cm-1. Anal. Calcd for C63H63Cl2N3P4STiW: C, 57.29; H, 4.81; N, 3.18. Found: C, 57.19; H, 4.79; N, 3.16. Preparation of [WCl(PMe2Ph)4(µ-N2)NbCpCl3]‚CH2Cl2‚ Et2O (10a‚CH2Cl2‚Et2O), [WCl(PMe2Ph)4(µ-N2)NbCp*Cl3]‚ C7H8 (10b‚C7H8), [WCl (PMe2Ph)4(µ-N2)TaCpCl3]‚CH2Cl2 (10c‚CH2Cl2), and [WCl(PMe2Ph)4(µ-N2)TaCp*Cl3] (10d). Complex 1 (4.20 g, 5.30 mmol) and [CpNbCl4] (1.59 g, 5.30 mmol) were dissolved in benzene (20 mL) at room temperature. With rapid evolution of nitrogen gas, the color of the solution changed from orange to black. The mixture was stirred for a further 30 min and evaporated under vacuum to give a black oil. The residual oil was dissolved in CH2Cl2, and the solution was filtered. Layering the CH2Cl2 solution with ether afforded black crystals of 10a‚CH2Cl2‚Et2O, which were collected, washed with ether, and dried in vacuo (5.48 g, 85% yield): 1H NMR (CDCl3) δ 1.61 (s, 24H, PMe), 6.37 (s, 5H, Cp), 7.127.48 (m, 20H, Ph); 31P{1H} NMR (CDCl3) δ -27.7 (s with 183W satellites, JWP ) 273 Hz); IR (KBr) 1395 (m) cm-1. Anal. Calcd for C42H61Cl6N2NbOP4W: C, 41.24; H, 5.03; N, 2.29. Found: C, 40.99; H, 4.84; N, 2.09. Complex 10b‚C7H8 was obtained in 98% yield as a dark green powder by the reaction of 1 with [Cp*NbCl4] and recrystallization from toluene/hexane: 1H NMR (C6D6) δ 1.56 (s, 24H, PMe), 2.26 (s, 15H, Cp*), 6.97-7.57 (m, 20H, Ph); 31P{1H} NMR (C6D6) δ -27.3 (s with 183W satellites, JWP ) 275 Hz); IR (KBr) 1385 (m) cm-1. Anal. Calcd for C49H67Cl4N2NbP4W: C, 47.98; H, 5.51; N, 2.28. Found: C, 47.89; H, 5.65; N, 2.04. Complex 10c‚CH2Cl2 was obtained in 74% yield as a dark red powder by the reaction of 1 with [CpTaCl4] followed by recrystallization from CH2Cl2/hexane: 1H NMR (CDCl3) δ 1.65 (s, 24H, PMe), 6.41 (s, 5H, Cp), 7.31-7.46 (m, 20H, Ph); 31P{1H} NMR (CDCl3) δ -24.6 (s with 183W satellites, JWP ) 275 Hz); IR (KBr) 1435 (m) cm-1. Anal. Calcd for C38H51Cl6N2P4TaW: C, 36.89; H, 4.15; N, 2.26. Found: C, 37.08; H, 4.27; N, 2.29. Complex 10d was obtained in 95% yield as a dark red powder by the reaction of 1 with [Cp*TaCl4] followed by recrystallization from toluene/hexane: 1H NMR (C6D6) δ 1.57 (s, 24H, PMe), 2.38 (s, 15H, Cp*), 6.98-7.42 (m, 20H, Ph); 31P{1H} NMR (C6D6) δ -24.9 (s with 183W satellites, JWP ) 277 Hz); IR (KBr) 1426 (m) cm-1. Anal. Calcd for C42H59Cl4N2P4TaW: C, 41.27; H, 4.86; N, 2.29. Found: C, 41.65; H, 5.09; N, 2.21. Dark red crystals of 10d‚2MeCN suitable for the crystal-

Ishino et al. lographic study were obtained by recrystallization of 10d from CH2Cl2-MeCN/ether. Preparation of [WCl(dppe)2(µ-N2)NbCpCl3]‚Et2O (11a‚ Et2O) and [WCl(dppe)2(µ-N2)TaCpCl3] (11b). Complex 2a (164.6 mg, 0.159 mmol) and [CpNbCl4] (47.6 mg, 0.159 mmol) were dissolved in THF (5 mL) at room temperature. With rapid evolution of nitrogen gas, the color of the solution immediately changed from orange to black. The mixture was stirred for a further 1 h, and the solvent was evaporated under vacuum to give a dark green solid. The residual solid was dissolved in CH2Cl2, and the solution was filtered. Slow diffusion of ether into the filtrate deposited black crystals of 11a‚Et2O (164.8 mg, 75% yield): 1H NMR (CDCl3) δ 2.68, 2.90 (br, 4H each, CH2 of dppe), 5.86 (s, 5H, Cp), 6.67-7.66 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 34.1 (s with 183W satellites, JWP ) 275 Hz); IR (KBr) 1383 (m) cm-1. Anal. Calcd for C61H63Cl4N2NbOP4W: C, 52.99; H, 4.59; N, 2.03. Found: C, 52.88; H, 4.22; N, 2.32. Complex 11b was prepared similarly from 2a and [CpTaCl4] as a brown powder in 46% yield: 1H NMR (CDCl3) δ 2.61, 2.87 (br, 4H each, CH2 of dppe), 5.86 (s, 5H, Cp), 6.68-7.69 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 36.9 (s with 183W satellites, JWP ) 281 Hz); IR (KBr) 1419 (m) cm-1. Anal. Calcd for C57H53Cl4N2P4TaW: C, 49.02; H, 3.83; N, 2.01. Found: C, 49.03; H, 4.02; N, 1.64. Preparation of [W(NCS)(dppe)2(µ-N2)NbCpCl3]‚THF (12a‚THF) and [W(NCS)(dppe)2(µ-N2)TaCpCl3] (12b). Complex 7 (186.1 mg, 0.142 mmol) and [CpNbCl4] (42.6 mg, 0.142 mmol) were dissolved in THF (3 mL), and the mixture was stirred for 1 h at room temperature. The resulting solution was filtered, and layering the THF solution with hexane afforded black crystals of 12a‚THF (179.0 mg, 90% yield): 1H NMR (CD2Cl2) δ 2.64, 2.83 (br, 4H each, CH2 of dppe), 5.84 (s, 5H, Cp), 6.55-7.60 (m, 40H, Ph); 31P{1H} NMR (CD2Cl2) δ 35.5 (s with 183W satellites, JWP ) 277 Hz); IR (KBr) 2029 (s), 1395 (m) cm-1. Anal. Calcd for C62H61Cl3N3NbOP4SW: C, 53.07; H, 4.38; N, 2.99. Found: C, 52.89; H, 4.24; N, 3.28. Complex 12b was prepared in 98% yield as a dark red powder by the reaction of 7 with [CpTaCl4] followed by recrystallization from toluene/hexane: 1H NMR (CD2Cl2) δ 2.55, 2.89 (br, 4H each, CH2 of dppe), 5.96 (s, 5H, Cp), 6.607.61 (m, 40H, Ph); 31P{1H} NMR (CD2Cl2) δ 37.4 (s with 183W satellites, JWP ) 281 Hz); IR (KBr) 2037 (s), 1420 (m) cm-1. Anal. Calcd for C58H53Cl3N3P4STaW: C, 49.09; H, 3.76; N, 2.96. Found: C, 49.02; H, 3.89; N, 2.67. Preparation of [WCl(PMe2Ph)3(tBuNC)(µ-N2)TaCp*Cl3] (13). Complex 9d (177.0 mg, 0.145 mmol) and tBuNC (70.1 mg, 0.236 mmol) were dissolved in ClCH2CH2Cl (3 mL), and the mixture was stirred for 10 h at 50 °C. The resulting solution was evaporated under vacuum, and the residual dark red solid was dissolved in toluene. Slow diffusion of hexane into the filtrated toluene solution deposited a red powder of 12 (44.0 mg, 26% yield): 1H NMR (C6D6) δ 0.95 (s, 9H, tBu), 1.29 (d, 6H, J ) 7.8 Hz, unique PMe), 1.78 (t, 6H, J ) 3.7 Hz, trans PMe), 1.80 (t, 6H, J ) 3.9 Hz, trans PMe), 2.30 (s, 15H, Cp*), 6.97-7.67 (m, 15H, Ph); 31P{1H} NMR (C6D6) δ -20.3 (d with 183W satellites, JWP ) 297 Hz, JPP′ ) 11 Hz), -24.4 (t with 183W satellites, JWP ) 260 Hz); IR (KBr) 2112 (m), 1458 (m) cm-1. Anal. Calcd for C39H57Cl4N3P3TaW: C, 40.12; H, 4.92; N, 3.60. Found: C, 40.34; H, 5.17; N, 3.98. Preparation of [WI(PMe2Ph)4(µ-N2)ZrCp2Me] (14a). Complex 1 (182.1 mg, 0.230 mmol), [Cp2ZrMeCl] (62.5 mg, 0.230 mmol), and NaI (418 mg, 2.79 mmol) were dissolved in toluene (5 mL), and the mixture was stirred for 20 h at 50 °C. The resulting reaction mixture was filtered, and the solvent was evaporated under vacuum to give a black solid. Recrystallization from CH2Cl2/hexane afforded 14a as a brown powder, which was collected, washed with hexane, and dried in vacuo (128.6 mg, 31% yield): 1H NMR (C6D6) δ 0.37 (s, 3H, ZrMe), 1.67 (s, 24H, PMe), 6.11 (s, 10H, Cp), 6.79-7.58 (m, 20H, Ph); 31P{1H} NMR (C6D6) δ -31.8 (s with 183W satellites,

Heterobimetallic Bridging Dinitrogen Complexes JWP ) 290 Hz); IR (KBr) 1541 (m) cm-1. Anal. Calcd for C43H57IN2P4WZr: C, 45.79; H, 5.09; N, 2.48. Found: C, 45.42; H, 5.33; N, 2.72. Preparation of [W(NCS)(dppe)2(µ-N2)ZrCp2Me] (14b). Complex 7 (225.0 mg, 0.172 mmol) and [Cp2ZrMeCl] (46.9 mg, 0.172 mmol) were dissolved in benzene (5 mL), and the mixture was stirred for 1 h at room temperature. Then the reaction mixture was evaporated under vacuum, and the residual black solid was extracted with THF. Layering the THF solution with hexane afforded black crystals of 14b (196.7 mg, 88% yield): 1H NMR (CDCl ) δ -0.02 (s, 3H, ZrMe), 2.32, 2.68 (br, 4H each, 3 CH2 of dppe), 5.66 (s, 10H, Cp), 6.48-7.66 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 45.8 (s with 183W satellites, JWP ) 297 Hz); IR (KBr) 2060 (s), 1557 (m) cm-1. Anal. Calcd for C64H61N3P4SWZr: C, 58.98; H, 4.72; N, 3.22. Found: C, 58.82; H, 4.63; N, 3.12. Preparation of [WCl(PMe2Ph)4(µ-N2)TaMe3Cl] (15a), [WCl(dppe)2(µ-N2)TaMe3Cl] (15b), and [MoCl(dppe)2(µN2)TaMe3Cl] (15c). Complex 1 (187.0 mg, 0.236 mmol) and [Me3TaCl2] (70.1 mg, 0.236 mmol) were dissolved in toluene (3 mL) at room temperature. With rapid evolution of nitrogen gas, the color of the solution changed from orange to black. The mixture was stirred for a further 30 min and filtered. Layering the filtrate with hexane afforded 15a as a brown powder, which was collected, washed with hexane, and dried in vacuo (165.7 mg, 66% yield): 1H NMR (C4D8O) δ 0.45 (s, 9H, TaMe), 1.68 (s, 24H, PMe), 6.94-7.44 (m, 20H, Ph); 31P{1H} NMR (C4D8O) δ -19.9 (s with 183W satellites, JWP ) 278 Hz); IR (KBr) 1480 (m) cm-1. Anal. Calcd for C35H53Cl2N2P4TaW: C, 39.61; H, 5.03; N, 2.64. Found: C, 40.00; H, 4.84; N, 2.29. Complex 15b was prepared similarly from 2a and [Me3TaCl2] in 55% yield: 1H NMR (C4D8O) δ 0.23 (s, 9H, TaMe), 2.41, 2.99 (br, 4H each, CH2 of dppe), 6.73-7.75 (m, 40H, Ph); 31P{1H} NMR (C D O) δ 42.0 (s with 183W satellites, J 4 8 WP ) 290 Hz); IR (KBr) 1470 (m) cm-1. Anal. Calcd for C55H57Cl2N2P4TaW: C, 50.60; H, 4.40; N, 2.15. Found: C, 50.55; H, 4.02; N, 1.99. Complex 15c was prepared in 59% yield as a black powder by the reaction of with 2b with [Me3TaCl2] and recrystallization from CH2Cl2/hexane: 1H NMR (C4D8O) δ 0.13 (s, 9H, TaMe), 2.46, 2.92 (br, 4H each, CH2 of dppe), 6.73-7.74 (m, 40H, Ph); 31P{1H} NMR (C4D8O) δ 55.5 (s); IR (KBr) 1483 (m) cm-1. Anal. Calcd for C55H57Cl2MoN2P4Ta: C, 54.25; H, 4.72; N, 2.30. Found: C, 53.99; H, 4.42; N, 1.93. Preparation of [WCl(dppe)2(µ-N2)NbMe2Cl2] (16a‚ CH2Cl2) and [MoCl(dppe)2(µ-N2)NbMe2Cl2] (16b). Complex 2a (360.8 mg, 0.348 mmol) and [Me2NbCl3] (79.8 mg, 0.348 mmol) were dissolved in benzene (3 mL) at room temperature. With rapid evolution of nitrogen gas, the color of the solution changed from orange to black. The mixture was stirred for a further 30 min, and the solvent was evaporated under vacuum to give a black solid. The residual solid was dissolved in CH2Cl2, and the solution was filtered. Layering the CH2Cl2 solution with hexane afforded black crystals of 16a‚CH2Cl2 (222.2 mg, 48% yield): 1H NMR (C6D6) δ 1.25 (s, 6H, NbMe), 2.28, 2.61 (br, 4H each, CH2 of dppe), 6.79-7.75 (m, 40H, Ph); 31P{1H} NMR (C6D6) δ 35.1 (s with 183W satellites, JWP ) 281 Hz); IR (KBr) 1406 (m) cm-1. Anal. Calcd for C55H56Cl5N2NbP4W: C, 49.93; H, 4.27; N, 2.12. Found: C, 50.27; H, 4.17; N, 1.73. Complex 16b was prepared from 2b and [Me2NbCl3] as a black powder in 74% yield by a similar procedure except that 16b was isolated by recrystallization from benzene/hexane: 1H NMR (CDCl3) δ 0.65 (s, 6H, NbMe), 2.44, 2.80 (br, 4H each, CH2 of dppe), 6.71-7.55 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 51.5 (s); IR (KBr) 1408 (m) cm-1. Anal. Calcd for C54H54Cl3MoN2NbP4: C, 56.39; H, 4.73; N, 2.44. Found: C, 56.50; H, 4.58; N, 2.04. Preparation of [WCl(dppe)2(µ-N2)TiCpS5]‚0.5Et2O (17‚ 0.5Et2O). To a dark yellow solution of Li2S5 prepared from S8 (0.046 mmol) and LiBEt3H (0.147 mmol) in THF (5 mL) was

Organometallics, Vol. 20, No. 1, 2001 197 added 5a‚CH2Cl2‚Et2O (90.4 mg, 0.065 mmol), and the resultant black solution was stirred for 24 h at room temperature. A brown solid precipitated during this period was filtered off, washed with a small amount of EtOH, and dried in vacuo. Recrystallization of this precipitate from CHCl3/ether deposited black crystals, which were collected, washed with ether, and dried in vacuo to give 17‚0.5Et2O (58.5 mg, 66% yield): 1H NMR (CDCl3) δ 2.50, 2.90 (br, 4H each, CH2 of dppe), 5.61 (s, 5H, Cp), 6.60-7.60 (m, 40H, Ph); 31P{1H} NMR (CDCl3) δ 42.0 (s with 183W satellites, JWP ) 290 Hz); IR (KBr) 1406 (m) cm-1. Anal. Calcd for C59H58ClN2O0.5P4S5TiW: C, 52.32; H, 4.32; N, 2.07. Found: C, 52.20; H, 4.63; N, 2.08. X-ray diffraction study of the crystalline sample clearly indicated that it contains 1.5 molecules of ether per one molecule of 17, but the crystals gave off a part of the ether molecules on drying under vacuum to give a sample with the empirical formula of 17‚0.5Et2O. Reaction of the Heterobimetallic Dinitrogen Complexes with H2SO4. In a typical run, concentrated H2SO4 (10 equiv) was added to a suspension of 10d (95.8 mg, 0.078 mmol) in MeOH (3 mL) under argon, and the mixture was stirred at room temperature for 3 h. The gaseous phase was analyzed by GLC, which showed that essentially no dinitrogen gas was evolved. Then the solution was dried up, and the amounts of ammonia and hydrazine included in the residue were determined as described previously.52 Crystallography. Single crystals of 4, 9a‚3CH2Cl2, 10a‚CH2Cl2‚Et2O, 10d‚2MeCN, 11a‚Et2O, 14b, and 17‚1.5Et2O suitable for X-ray analyses were sealed in Pyrex glass capillaries under an argon atmosphere and used for data collection. Diffraction data were collected on a Rigaku AFC-7R four-circle automated diffractometer with Mo KR (λ ) 0.71069 Å) radiation and a graphite monochromator at 21 °C using the ω-2θ scan technique. Empirical absorption correction based on ψ scans and Lorentz-polarization correction were applied. For compounds 9a‚3CH2Cl2, 10a‚CH2Cl2‚Et2O, 10d‚2MeCN, 11a‚Et2O, and 14b, decay (17.57, 3.35, 17.33, 6.14, and 9.62%, respectively) was observed during the data collection, and a correction for decay was applied in each case. Details of the X-ray diffraction study are summarized in Tables 5 and 6. The structure solution and refinements were performed by using the teXsan program package.53 The positions of the nonhydrogen atoms were determined by direct methods (SIR 9254 for 9a‚3CH2Cl2) or by Patterson methods (DIRDIF PATTY55 for the others) and expanded using Fourier techniques. The CH2Cl2 molecules in 9a‚3CH2Cl2, the CH2Cl2 and ether molecules in 10a‚CH2Cl2‚Et2O, and the MeCN molecules in 10d‚ 2MeCN showed signs of disorder and could not be refined satisfactorily. The non-hydrogen atoms of these solvent molecules were found from the difference Fourier maps and included in the refinement with fixed isotropic parameters. One of the ether molecules in 17‚1.5Et2O was found to be located on the center of symmetry. The carbon and oxygen atoms of this ether molecule were included in the refinement as fixed atoms, where the disordered methylene carbon atoms were considered to have the occupancies of 50%. Isotropic thermal parameters were used for the carbon and oxygen atoms of the ether molecule in 11a‚Et2O. All other nonhydrogen atoms were refined by full-matrix least-squares techniques with anisotropic thermal parameters, and the hydrogen atoms except for those of the solvent molecules in (52) Takahashi, T.; Mizobe, Y.; Sato, M.; Uchida, Y.; Hidai, M. J. Am. Chem. Soc. 1980, 102, 7461-7475. (53) teXsan: Crystal Structure Analysis Package; Molecular Structure Corp.: The Woodlands, TX, 1985 and 1992. (54) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.; Giacovazzo, C.; Guagliardi, A.; Polidori, G. J. Appl. Crystallogr. 1994, 27, 435. (55) PATTY: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The DIRDIF program system; Technical Report of the Crystallography Laboratory; University of Nijmegen: Nijmegen, The Netherlands, 1992.

198

Organometallics, Vol. 20, No. 1, 2001

Ishino et al.

Table 5. Crystallographic Data for 4, 9a‚3CH2Cl2, 10a‚CH2Cl2‚Et2O, and 10d‚2MeCN formula fw space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z dcalc, g cm-3 µcalc, cm-1 Ra Rwb a

4

9a‚3CH2Cl2

10a‚CH2Cl2‚Et2O

10d‚2MeCN

C37H49Cl3N2P4TiW 983.81 Cc 15.563(2) 16.800(1) 15.932(2)

C61H59Cl8N3P4STiW 1505.49 P1h 12.290(2) 13.700(3) 20.359(4) 98.86(2) 106.33(1) 93.63(2) 3229(1) 2 1.548 24.08 0.068 0.070

C42H61Cl6N2NbOP4W 1223.33 P21/n 10.753(5) 22.320(6) 21.467(6)

C46H65Cl4N4P4TaW 1304.55 P1 h 11.917(2) 12.769(3) 18.984(3) 87.14(1) 89.32(1) 66.33(1) 2642.4(8) 2 1.640 46.01 0.040 0.041

92.36(1) 4162.1(8) 4 1.570 33.31 0.027 0.032

99.39(4) 5083(3) 4 1.598 29.63 0.050 0.061

R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(Fo| - |Fc|)2/∑wFo2]1/2, w ) 1/σ2(Fo).

Table 6. Crystallographic Data for 11a‚Et2O, 14b, and 17‚1.5Et2O formula fw space group a, Å b, Å c, Å β, deg V, Å3 Z dcalc, g cm-3 µcalc, cm-1 Ra Rwb a

11a‚Et2O

14b

17‚1.5Et2O

C61H63Cl4N2NbOP4W 1382.65 P21/n 19.539(4) 14.883(2) 20.185(4) 90.31(2) 5869(1) 4 1.564 24.89 0.044 0.047

C64H61N3P4SWZr 1303.23 P21/a 17.815(4) 17.584(4) 18.606(4) 95.57(2) 5800(2) 4 1.492 23.52 0.037 0.036

C63H68ClN2O1.5P4S5TiW 1428.64 P21/n 13.531(2) 18.472(4) 25.416(2) 98.477(8) 6283(1) 4 1.510 23.12 0.049 0.038

R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(|Fo| - |Fc|)2/∑wFo2]1/2, w ) 1/σ2(Fo).

10a‚CH2Cl2‚Et2O and the disordered ether molecule in 17‚ 1.5Et2O were included in the refinements with fixed isotropic parameters.

Acknowledgment. This work was supported by a Grant-in-Aid for Specially Promoted Research (09102004) from the Ministry of Education, Science, Sports, and Culture, Japan.

Supporting Information Available: Tables of atom coordinates, anisotropic thermal parameters, and bond distances and angles for 4, 9a‚3CH2Cl2, 10a‚CH2Cl2‚Et2O, 10d‚ 2MeCN, 11a‚Et2O, 14b, and 17‚1.5Et2O. This material is available free of charge via the Internet at http://pubs.acs.org. OM000684J